Drilling apparatus



J. E. Hor-'Foss Y 2,212,067

DRILLING APPARATUS Fiied Marchzo, 1959` Aug. 2 0, 194,0.

2 Sheets-Sheet 1 All@ 20 1940- J. E. HoFFoss 2,212,067

DRILLING APPARATUS Filed March 20. 19:59 2 sheets-shan 2 Patented Aug. 20, 1940 IUNITED STATES 2,212,061 DRILLING APPARATUS.

John E. Hof'foss, Houston, Telt., assignor to Reed Roller Bit Company, Houston, Tex., a corporation of Texas Application March 20, 1939, Serial No. 262,888

claims. (C1. 25a-7s) 'I'his invention relates to drilling equipment, and more particularly has reference -to reaming and coring'devices for use in drilling wells in earth formations,

The general object of this invention is to provide a device whereby a core may be taken from the formation at the bottom 'of a well being drilled without the likelihood or forming a crooked hole or encountering Iother diiilculties usually found in taking cores. i

The ordinary procedure 4in coring a well is to run a core drill of a size smaller than the hole which has been drilled up to the taking of the core. This is what is commonly known as ratholing ahead. The purpose of drilling such a smaller hole at the bottom of a-main hole is to providel la seat at the bottom of the main hole against which a test tool may be set for drill stem testing after the core has been taken.

However, in attempting to cut a rat-hole ora f hole of smaller diameter in the bottom of the main hole difficulty has been encountered in/that when a smaller bit is lowered to the bottom of the main hole and rotated it will tendto start 25 cutting at one side of the main hole rather than at the center thereof. 'I'he rat-hole will thus start out eccentric withrespect to the main hole and in addition to starting a crooked hole, this will leave an eccentric seat for a testing tool such 30 as above referred to. In the event that casing is set at this point, the cement which is employed about the lower end of the casing will be all on one side of the casing and the possibili/1Qv of a, leak past the cement seal will be greatly increased. Furthermore, if a test tool is run into the hole and an attempt made to test the formation by seating it on the lower end of the main hole with th/e testing tool projecting into the rat-hole, it will b// ound almost impossible to obtain a perfect seal with respect to the formation-if the formation is firm or hard. On the other hand, if the formation is'soft, the testing tool may be forced in but in many instances it will be stuck thereby and it will be foundlater to be impossible to pull 45 it out of the hole.-

It is, therefore, anobject" of this invention' to provide a device which will .make it possible to form a rat-hole concentric with the bottom of the possible to form a more -perfect seat for a testing tool at the-bottom of the main hole of a well. Another object of this invention is-to make itl possible to continue drilling as long as desired with a-rat-hole forming bit and provide a structure thereabove which will act both as a guide for, such bit and as a reamer for enlarging the rathole to the size of the main hole-,-

-Otherfobjects and advantages'of this invention will become apparent from the following descrip- 10 tion taken in connection with the following drawings:

In the drawings: i 1 Y Fig. 1 is a vertical cross section through the bottom of a well hole showing the effect of or- 15 dinary rat-holing and coring methods and apparatus. .s

Fig. 2 is asimilar view showing the start of a rat-holing or coring operation employing the present invention. 7 20 Fig. 3 isV a similar View showing the well hole and apparatus of Fig. 2 after the drilling has proceeded until the rat-hole is cutto its ultimate depth.

Fig. 4 is a top plan view of theguiding member 25 employed in accordance with this invention. Fig. 5 is an inside elevation of one section of the guiding and reaming device shown in Fig. 4. Referring agai'n to Fig, 1, the main hole which has been drilled prior to the coring or rat-heling operation is designated by the numeral l. After this hole has been completed down to the point 2, the core bit 3 which is of smaller diameter than the main hole I is lowered on the drill collar 4 and the usual drill stem. Drilling is then started but/ 35 '-Ydue to the fact that there is no positive means for centeringthe bit 3 on the bottom 2 of the main hole, the bit will tend to dig in .at one side of the `rnain hole and form an eccentric rat-hole 5. It wilt Veadily be seen that with suchia hole, itv will not only be impossible to Aform a perfect seat for a testing tool on the bottom of the main holeA about the upper end of the rat-hole,fbut also when drilling is again resumed withthe bit of larger diameter, the presence of -the eccentric rat-hole will tend to deflect the path of the larger bit and cause the drilling of a-crooked hole.

In Fig. 2 is illustrated the operation of a device constructed in accordance with the present invention. In this figure the core bit 3 is lowered on a drill collar 6 which is similar to the drill collar 4 but differs in that it is provided with a relatively square upwardlyiacing shoulder 'l adjacent its lower end and with al reduced portion 8 intermediate its lower and upper ends. Adjacent its upper end the diameter is again increased as shown at Il but the change in diameter between the portions 8 and!! is accomplished not by an annular shoulder but by an irregularly formed. `shoulder having downwardly projecting parts II) vand upwardly projecting grooves I I therebetween Y which is illustrated more in detail in Figs. 4 and '5. This member consists of two sections I3 and I4 which are substantially identical and each vof which is provided with an ear I5 adjacent one end thereof for a purpose presently to be described. Each'of these sections is substantially in the form of a semi-cylinder and -is provided intermediate its extremities with a radially p ro- 'Ijecting blade I6 which operates as a reamer.

Each of these sections is also provided with a second radially projecting blade substantially at one extremity thereof as shown at ITI and adapted to be opposed to the eark I5 onv the other section. These opposed blades and ears I5 and I1 are provided with apertures for the reception of bolts III which cooperate with nuts I9 to secure the two sections together about the reduced portion 8 of.v

the drill collar. Each of the sections I3 and I4 is also provided with a threaded opening adapted to receive a screwed in shear pin 20 and the drill collar is provided: with openings 2l for the re` ception of 'suchshear pins. The sections I3 and I4 are also provided adjacent their upper ends with grooves 22 and splines 23 adapted to engage the grooves and splines II and I on the drill collar when this element is moved upwardly to its uppermost position on the drill collar. If desired, bearing rings 24 of rubber or other suitable material maybe mounted lin grooves in the sections to provide a sliding contact with the drill collar.

The operation of the device is as follows:

. Before lowering the core barrel and drill collar into the well on the usual drill stem, the guiding and reaming member shown in Figs. 4 and 5 is secured about'the drill 'collar in the position shown in Fig. 2. The shear pins 20 are then put in place so as to retain this guiding member in this position .on the drill collar during the lowering thereof. When the device reaches the bot-r reaming tool of large'r overall diameter than said drilling tool slidably mounted above said drilling tom of the main hole, the reaming and guide member which will be in contact with the side walls of the hole will serve to center the smaller bit 3 so that when rotation begins-the smaller bit will begin to dig in substantially concentrically with respect to the main hole, thus forming a concentric rat-hole as shown at 24`in Figs. 2 and 3. As this drilling progresses -the guiding member will move downwardly with the drill stem until it comes in contact 'with the shoulder at the bottom of the main hole, whereupon its blades Iwill begin to dig in causing it to drag back and then to move upwardly with respect to the drill collar. This will cause the shearing of shown in Fig. 3. The drill collar will then have\ moved downwardly through the guiding and reaming deviceuntill the splines I0 and II engage the splines 22 and 23, whereupon theguiding and reaming member will again begin to rotate with the drill stem and will be forced downward-- ly with the drill stem. This will result rst in facing the bottom of the main hole so as to provide a perfect seat for any testing tool or the like which may be later loweed'into the hole, and will thereafter continue to ream the smaller hole to the size of th'e larger hole as the drilling progresses. It will thus be seen that `a core of any length may be tak seat which will be formed for a testingltool to be `subsequently lowered. At the same'time, all of l`above the lower end thereof and slidable upward- .ly with respect thereto, frangible means for holding said guiding member in its lowermostpos-l tion while being lowered into a well, said vguiding member having reaming blades thereon adapted to enlarge the size of the drilled hole. r

2. In a drilling apparatus, a drilling tool, aV

guiding member carried by said drilling tool above the lower end thereof and slidable upwardly with respect thereto, said guiding member having parts without leaving too much o! a rat-hole and without in any way impairing thev of greater overall diameter than the hole adapted to. be formed by said drilling tool, and frangible means for holding saidy guiding member in its lowermost position while being lowered into a Well.

3. In a drilling apparatus, a drilling tool, a. reaming tool of larger overall diameter than said drilling tool slidably mounted above said drilling tool for limited sliding movement, means for releas'ably holding said reaming tool in a lower position with respect to the drilling'tool while being lowered into -a well, and means for locking said reaming tool against rotation with respect to said drilling tool when in its uppermost position.

4. In a drilling apparatus. a drilling tool,- a

tool for limited sliding movement, and means for locking saidreaming tool against rotation with iss respect to said drilling tool only when said reaming tool is in its uppermost position.

5. In a drilling apparatus, adrilling tool, a reaming tool of larger overall diameter than said drilling tool slidably and rotatably mounted above said drilling tool for limited sliding'movement, and means for locking saidreaming tool against rotation with respect to said drilling tool only 'when said reaming tool is in its uppermost position. .r l JOI-IN E. HOFFOSS. 

